USPTO Patents Application 09896990

MPY-22-2003 15=46 eCLT BPYTOUN

SUBSTITUTE
SPECIFICATION
AND CLAIMS

Received from < 281 8342911 > at 5/22/03 4:19:56 PM [Eastern Daylight Time]

MAY-22-2003 15=46

ft

T BAYTOLJN

281 8342911

P. 37

2001B053US

BIAXIALLY ORIENTED, METALLIZED HERMETICALLY
SEALABLE FILMS INCLUDING NON-MIGRATORY SLIP AGENT

TECHNICAL FIELD

[0001] This invention relates generally to multilayer films containing materials
that deliver acceptable coefficient of friction (COF) without substantially
diminishing the ability of a film to be metallized, while providing a hermetic seal.
More specifically this multilayer film has a non-migratory slip agent in one outer-
most layer.

BACKGROUND

[0002] In the packaging of certain types of foods, such as snack foods, including
candies, potato chips, cookies and the like, it is common practice to employ a
multi-layer film. Polypropylene films are widely used in the packaging industry
due to their superior physical properties, such as transparency, stiffness, moisture
barrier characteristics and others. Despite these highly desirable properties,
unmodified polypropylene film has the property of having a high inherent
coefficient of friction and film-to-film destructive blocking on storage. This high
film-to-film coefficient of friction makes polypropylene films difficult to employ
in automatic packaging equipment in their unmodified form.
[0003] Coefficient of friction characteristics of polypropylene and other
thermoplastic films may be modified by the inclusion of slip agents in the
polymer. Most of these slip agents are migratory, such as polydialkyl siloxane or
fatty amides, such as, erucamide and oleamide. Although they do reduce the
coefficient of friction, their effectiveness depends upon the ability to migrate to
the surface of the film. The development of the desired low coefficient of friction
value is dependent upon the type and amounts of amides, and time and
temperature aging effects. Even the heat history of the film, while in storage and
shipping and during subsequent converter processes, effects the coefficient of
friction. In addition, the presence of these types of fatty acid amides on the film
surface results in adverse appearance effects manifested by an increase in haze, a

Received from < 231 834291 1 > at 5C2/03 4:19:56 PM [Eastern Daylight Time]

MflY-22-2003 15:46

ECLT BPYTOUJN

281 8342911 P. 38

2001BO53US

2

decrease in gloss and the presence of streaks. These materials also adversely
effect the wettability and adhesion of solvent and water-based inks, coatings and
adhesives, as well as potentially negatively effecting adhesion of metal and/or
coatings.

[0004] In PCT US94/14280 a film structure containing a non-migratory
particulate crosslinked hydrocarbyl-substituted poiysiloxane slip agent is
described. The film structure includes at least one layer of an olefin homo-, co- or
terpolymer having a surface-treated external surface which is printable, sealable
and machinable and as combined slip agent and antiblock a non-migratory
particulate crosslinked hydrocarbyl-substituted poiysiloxane, and/or liquid
polydimethyl siloxane.

[0005] Additional descriptions of olefinic polymer films in which particulate
siloxane resins are employed to provide improved films will be found in U.S. Pat.
Nos. 4,966,933; 4,769,418; 4,652,618; and 4,594,134.

[0006] US. Pat. No. 4,966,933 suggests a propylene polymer film containing a
propylene polymer, a fine powder of a crosslinked silicone resin and a hydroxy-
fatty acid glyceride. The provided amounts of fine powder of silicone resin and
hydroxy-fatty acid glyceride in the metallization layer are required for adaptability
to vacuum deposition. Example 3 provides a two-layer coextruded film in which
the fine powder of crosslinked silicone resin is compounded with polypropylene
homopolymer to form a metallization layer (B) and the fine powder of crosslinked
silicone resin is compounded with an ethylene/propylene/butene-1 copolymer to
form a skin layer (a). The ratio of reported particle size to skin thickness is about
0.143 for skin layer (B) and about 1 .29 for skin layer (A).

SUMMARY

[0007] We have discovered that non-migratory polymethylacrylate slip agents,
when included into a seal layer of a three layer multilayer film, provide a film
with acceptable COF, without substantially diminishing the ability of the films to
be metallized.

Received from<281 8342911 > at 5/22/03 4:19:56 PM [Eastern DayOght Time]

MAY-22-2003 15 : 46

ECLT BflYTOUN

281 8342911 P. 39

200IB053US

3

[0008] More specifically, embodiments of our invention provide a film structure
which includes an olefinic polymer core layer having at least one sealant skin
layer comprising an olefin polymer, having an external surface which is sealable,
the sealant skin layer containing a non-migratory particulate.
[0009] On the other surface of the olefin polymer core layer there is a
metallizable layer having an external surface, which is substantially free of the
non-migratory particulate, polymethylmethacrylate (PMMA). The non-migratory
slip agent does not, generally, effect film barrier properties or lamination bond
strengths to other oriented polypropylene based films or polyester based films that
might be laminated thereto.

[0010] In other embodiments the invention relates to a film structure comprising
a first sealant skin layer (a) of an olefin co- or ter-polymer on one side of a core
layer (b), the first sealant skin layer containing a non-migratory particulate. On an
opposite side of the core layer there is a second skin layer (c) 3 which may include
an ethylene homopolymer, which is substantially free of the particulate PMMA of
the first sealant skin layer. In further embodiments of our invention, the film
structure is a three layer film.

[0011] Embodiments of our invention further relate to a method of making a
film comprising the step of coextruding a film structure, the film structure
comprising a heat sealable layer (a) comprising an olefinic co- or teipolymer
containing a particulate PMMA; a core layer (b) comprising an olefinic polymer
and an outer layer (c) comprising an ethylene homopolymer which is substantially
free of the particulate PMMA of layer (a).

[0012] These and other aspects, features and advantages of embodiments of the
present invention will become better understood with reference to the following
description and appended claims.

DETAILED DESCRIPTION

[0013] In certain embodiments of our invention, non-migratory slip agent
containing multilayer films are contemplated. The non-migratory slip agent will

Received from < 281 8342911 > at 5/22/034:19:56 PM [Eastern Daylight Time]

MftY-22-2003 15:47

ECLT BAYTOUN

281 8342911 P. 40

2001B053US

4

generally be in a seal layer* These multilayer films will exhibit an acceptable
COF as well as excellent metal liability characteristics, as compared to multilayer
films containing migratory slip.

10014] The combination of acceptable COF and excellent metallizability, along
with excellent sealability, will be especially useful in packaging films, more
particularly snack packaging, although other uses are contemplated.
[0015] Following is a detailed description of certain preferred combinations of
non-migratory slip containing multilayer films, their fabrication into useful
articles, and use of these articles. Those skilled in the art will appreciate that
numerous modifications to these preferred embodiments may be made without
departing from the scope of our invention. For example, while certain specific
non-migratory slip containing films are exemplified, other non-migratory slip
containing films are also contemplated.

{0016] To the extent that this description is specific, it is solely for the purpose
of illustrating certain preferred embodiments of the invention and should not be
taken as limiting the present inventive concepts to these specific embodiments.
(0017] More specifically, embodiments of our invention provides a film
structure which includes a core layer having at least one sealant skin layer
contiguous to a surface of the core layer, the sealant skin layer comprising an
olefin polymer having an external surface which is sealable and machinable, the
sealant skin layer containing a particulate non-migratory slip system which
provides improved antiblock and/or slip properties. The particulate non-migratory
slip system includes non-migratory PMMA particles.

[0018] On the other side of the core layer there may be metallizable layer
having an external surface, which is substantially free of the non-migratory slip
agent. By substantially free, we intend < 5, or < 2, or < 1, or < 0.5, or 0 weight
percent of the non-migratory slip, based on the weight of the metallizable layer.
The non-migratory slip agent does not generally effect film barrier properties or
lamination bond strengths to other oriented polypropylene based films or polyester
based films. In one embodiment of the invention, this non-migratory slip agent

Received from < 231 8342911 > at »22/03 4:19:56 PM [Eastern Daylight Time]

MAY-22-20B3 15:47

ECLT BAYTOUN

281 8342911 P. 41

2001B053US

5

containing film layer may be metallized on its outermost surface. We have found
that the non-migratory slip agent included in the sealant layer may reduce
scratching of the metal surface when the film is wound into a roll.
[0019) Embodiments of the invention relate to a film structure including a first
sealant skin layer (a) of an olefin co- or ter-polymer having an external surface
which is sealable on one side of a core layer (b), the first sealant skin layer
containing an non-migratory slip agent, including a non-migratory PMMA, on an
opposite side of the core layer there is a second skin layer (c) which includes an
ethylene homopolymer which is substantially free of the non-migratory slip agent
of the first sealant skin layer, the second skin layer, optionally, having a metal
deposited thereon.

[0020] Embodiments of the invention further relate to a method of making a
film comprising the steps of coextruding a film structure, the film structure
comprising a heat sealable layer (a) comprising an olefinic co- or terpolymer
containing an non-migratory slip agent, including PMMA particles; a core layer
(b) including an olefinic polymer and a layer (c) further including an ethylene
homopolymer which is substantially free of the non-migratory slip agent of layer
(a); and, optionally, metallizing the surface of the layer (c) by depositing a metal
thereon.

Core Layer

[0021] The core layer of the multilayer films of embodiments of our invention
may include isotactic polypropylene. The core layer will have a first and a second
surface.

[0022] Isotactic polypropylene (iPP) contemplated in embodiments of our
invention include those iPPs made using either Ziegler-Natta or metallocene
catalysts or combinations thereof While generally contemplating homo isotactic
polypropylene, random and impact copolymer polypropylenes are also
contemplated with an ethylene, a-olefin s diolefin or combinations thereof, content
up to 10% (wt).

Received from < 281 834»11 > at »22/03 4:19:56 PM [Eastern Daylight Time]

MAY-22-2083 15:47

ECLT BPYTOUN

281 8342911 P. 42

200IB053US

6

(0023] MFRs of the iPP may range from 0.1 to 1000, or 1 to 500, or 10 to 250 3
or 10 to 100 dg/min.

[0024J The core layer of embodiments of our invention will have a thickness in
the total film in the range of from 3-20 urn, or 5-18 jim, or 5-15 |im. Generally
the core layer will be present in the total film in the range of from 20-60 weight
percent, or in the range of from 30-50 weight percent, based on the total weight of
the film.

[0025] Moreover, although skin layers are referred to, the skin layers may have
additional structures bonded thereto, based on the functional requirements of the
overall structure. Such materials bonded thereto will generally further enhance
the present three layer structure for specific uses.

[0026} When an opaque label or film structure is desired, the core layer of the
film structure of the present invention may be formed in accordance with U.S. Pat.
No. 4,377,616,

[0027] Where opacifying agents are desired, they may be incorporated in the
core layer, in a proportion of up to 10 %, or up to 5 %, or up to 1 %, by weight,
based on the total weight of the core layer. Suitable conventional opacifying
agents can be added to the melt mixture of the core layer before extrusion.
Opacifying compounds are generally well known. They may be exemplified by
iron oxides, carbon black, aluminum, aluminum oxide, titanium dioxide, and talc.
[0028| The core layer may be an oriented polypropylene film. The orientation
may be uniaxial, or biaxial. Further, in other embodiments, the film structure may
be oriented subsequent to application of any layer, or may be oriented after the
structure is complete.

[0029] The total film will have a thickness in the range of from 10-40 or 15-35
jam.

First Sealant Skin Layer

[0030] A first sealant skin layer will be contiguous to a first surface of the core
layer in embodiments of our invention. The polymer materials, which are

Received from < 281 834^1 1 > at »22^03 4:19:56 PM [Eastern Daylight Time]

MAY-22-2003 15:47

ECLT BAYTOUN

281 8342911 P. 43

2001B053US

7

contemplated for use in forming this first sealant skin layer, are suitably
exemplified by heat sealable polyolefinic copolymers and teipolymers and blends
thereof The copolymers are exemplified by and include, but are not limited to,
block copolymers, for example of ethylene and propylene, random copolymers.
The terpolymers are exemplified by ethylene-propylene-butene-1 terpolymers.
Also, heat sealable blends can be utilized in providing layer (a). Thus, along with
the copolymer or teipolymer, there can be polypropylene homopolymer, e.g. one
which is the same as, or different from, the isotactic polypropylene of the core
layer (b) or other material which does not impair the heat sealability of this layer.
The first sealant skin layer may additionally or alternatively include, but is not
limited to, materials selected from one or more of ethylene propylene random
copolymers (EP rep), propylene butene copolymer (PB), low density polyethylene
(LDPE), linear low density polyethylene (LLDPE), medium density polyethylene
(MDPE), or combinations thereof.

[0031] The first sealant skin layer has a thickness in the range of from 3-25 nm,
or 3-20 \xm, or 5.5-10 fxra, or expressed alternatively, the first sealant skin layer
will be present in the total film in the range of from 10-70, or 10-60, or 15-60
weight percent, based on the total weight of the film.

[0032] The first sealant skin layer also includes a non-migratory slip agent,
polymethyl methacrylate (PMMA).

[0033] The non-migratory slip agent will have a (mean) particle size in the
range of from 5^25 jam, or 7-20 Jim, or 10-18 *im. Alternatively, the size of the
particles in the non-migratory slip agent, such as PMMA, may be greater than
20% of the thickness of the first sealant skin layer, or greater than 40% of the
thickness of the first sealant skin layer, or greater than 50% of the thickness of the
first sealant skin layer. The size of the particles of such non-migratory slip agent
may also be at least 10% greater than the thickness of the first sealant skin layer,
or at least 15% greater than the thickness of the first sealant skin layer, or at least
20% greater than the thickness of the first sealant skin layer, or at least 40%
greater than the thickness of the first sealant skin layer.

Received from < 281 8342911 > at M22/03 4:19:56 PM [Eastern Daylight Time]

MAY-22-2003 15=48

ECLT BAYTOUN

281 8342911 P. 44

2001B053US

8

[0034J Suitable ethylene-propylene-butene-1 (EPB) terpolymers are those
obtained from the random inter-polymerization of from 1-8 weight percent
ethylene, or from 3-7 weight percent ethylene with from 1-10 weight percent
butene-1, or from 2-8 weight percent butene-1 with propylene representing the
balance. The foregoing EPB terpolymers may have a melt index at 230°C of from
2-16, or from 3-7 dg/min, a crystalline melting point of from 100° C-140°C, an
average molecular weight of from 25,000-100,000 and a density within the range
of from 0.89-0.92 gm/cm3.

[0035J Generally, there will be no separate layer between the core layer and the
first sealant skin layer, although such layer is not prohibited

Second Skin Layer

[0036] The second skin layer of embodiments of our invention will generally be
contiguous to a second surface of the core layer. Contemplated for use in forming
the second skin layer may be metallizable polymeric materials. Typical examples
of such materials are those selected from one of, ethylene polymers such as linear
low density polyethylene (LLDPE), low density polyethylene (LDPE), medium
density polyethylene (MDPE), high density polyethylene (HDPE) or blends
thereof Other contemplated metallizable resins include ethylene-vinyl alcohol
copolymer (EVOH), ethylene-viny] acetate copolymer (EVA) and polypropylene
homopolymer. The second skin layer may have a thickness in the range of from
1.5-12 nm, or 2.5-10 |xm, or the second skin layer may be present in the total film
in the range of from 10-40 or 12-35 weight percent, based on the total weight of
the film.

f0037J This second skin layer may be formed without adding the non-migratory
slip, which is included in the first sealant skin layer. Thus, the second skin layer
is considered to be substantially free of the non-migratory slip used in first sealant
skin layer. This does not however, exclude the incidental presence of components
of the non-migratory slip which might occur upon subsequent handling of the
finished film, for example upon winding the film onto a roll, whereby non-

Recerved from < 281 834291 1 > at 5/22J03 4: 19:56 PM [Eastern Daylight Time]

MAY-22-2003 15=48

ECLT BAYTOUJN

281 8342911 P. 45

2001B053US

9

migratory particles from the first sealant skin layer might be sloughed onto the
external surface of or imbedded into the second skin layer.
[0038] The second skin layer may be metallized. Prior to metallization, the
second skin layer may be treated with one of flame, polarized flame, or corona.

Non-Migratory Slip

[0039] Migratory slip agents, such as polydtalkyl siloxane, fatty amides, and the
like* are not considered part of embodiments of our invention, as by their nature
they can migrate to the surface of a layer to be metallized and either make
depositing metal difficult or lead to partial delamination of the metal from the film
surface. In embodiments of our invention, the non-migratory slip agent will be
present in the first sealant skin layer in the range of from 500-10,000 ppm, or
1000-8000 ppm, or 1200-6000 ppm, or 1500-4000 ppm, based on the total weight
of the layer containing the non-migratory slip.

[0040] Prior to extrusion, in accordance with embodiments of the present
invention, the first sealant skin layer may be compounded with an effective
amount of a non-migratory slip.

[0041] Particulate, generally spherical materials, including PMMA resins, such
as EPOSTAR®, manufactured by Nippon Shokubai Co., Ltd., are contemplated.
Other commercial sources of similar suitable materials are also known to exist.
By non-migratory, we intend that these particulates do not generally change
location throughout the layers of the film in the manner of the migratory slip
agents.

Heat Seals/Seal Strength

[0042] Heat seals in packaging can generally be lap, fin or crimp. Most
frequently, vertical form fill and seal and/or horizontal form fill and seal (VFFS
and/or HFFS, respectively) useful in snack packaging will employ a fin seal and
two crimp seals. For extended shelf life, a hermetic seal is desirable, one that does
not permit the passage of gas.

Received from < 281 8312911 > at 5/22/03 4:19:56 PM [Eastern Daylight Time]

MPY-22-2003 15:48

ECLT BPYTQUN

281 8342911 P. 46

2001B053US

10

Metallization

[0043) In another embodiment, the exposed surface of the second skin layer
may be metallized. This occurs by application of a thin layer of metal. Metal
deposition techniques are well known in the art. Typically, the metal layer is
applied to an optical density of 1.5-5.0, or 1.8-2.6. Optical density provides a
determination of the absorption of visual light and is determined by standard
techniques. To obtain the optical density values of the instant films a commercial
densitometer was used such a Macbeth model TD 932, Tobias Densitometer
model TDX or Macbeth model TD903. The densitometer is set to zero with no
film specimen. A film specimen is placed over the aperture plate of the
densitometer with the test surface facing upwards. The probe aim is pressed down
and the resulting optical density value is recorded.

[0044] Usually vacuum deposition is the method of choice for metallizing the
film. While aluminum is a contemplated metal, other metals, e.g. zinc, gold,
silver, etc. which are capable of being deposited to the surface of the film can also
be employed.

[00451 Typically, prior to metallization, the surface of the second skin layer may
be treated to improve metal adhesion by corona, plasma, flame, or polarized
flame.

[0046J The resulting metallized film has low water vapor transmission rate
characteristics and low oxygen transmission rate characteristics. These improved
physical properties make the film ideally suited for packaging food products, even
those comprising liquids.

Orientation

(0047] Embodiments of our invention include possible orientation of the
multilayer films. Orientation in the direction of extrusion is known as machine
direction orientation (MD), orientation perpendicular to direction of extrusion is
known as transverse direction (TD). Orientation may be accomplished by
stretching or pulling a blown film in the MD, using the blow-up ratio to

Received from < 281 834^11 > at 5/22/03 4:19:56 PM [Eastern Daylight Time]

MftY-22-2003 15:49

ECLT BAYTOLJN

281 8342911 P. 47

200IBO53US

11

accomplish TD orientation, or both may be used. Blown films or cast films may
also be oriented by a tenter frame orientation subsequent to the film formation
process, again in one or both directions. Orientation ratios may generally be in the
range of 1 : 1-1 : 1 5 or MD 1 :4-l r 1 0 or in TD 1 :7-l : 12. Orientation may occur after
any layer is added. Orientation may be limited to use of a biaxially oriented
polypropylene film as the core layer.

Other Ingredients

[0048] Other ingredients in our inventive blends include, but are not limited to,
pigments, colorants, antioxidants, antiozonants, antifogs, antistats, fillers such as
calcium carbonate, diatomaceous earth, carbon black, combinations thereof, and
the like,

[0049J Either or both skin layers can also contain pigments, fillers, stabilizers,
light protective agents or other suitable modifying ingredients if desired. Further,
either or both skin layers can optionally contain a minor amount of an antiblock
material, such as, clays, talc, glass, and the like. These antiblock materials can be
used alone, or different sizes and shapes can be blended to optimize machinability.
[0050] The core layer can contain anti-static agents, e.g„ cocoamine or
N,N bi$(2-hydroxyethyl) sterylamine. Suitable amines include mono-, di, or
tertiary amines.

Definitions and Testing Protocols

[0D51] Melt Flow Rate (MFR): ASTM D 1238, condition L
Melt Index (MI): ASTM D 1238, condition E

Experimental
[0052J Materials:

Chisso 7701, available from Chisso Cotporation, an ethylene-propylene-

butene-1 teipolymer,

Received from < 281 8342911 > at 5/2Z r 03 4:19:56 PM [Eastern Daylight Tune]

MAY-22-2003 15:49

ECLT BAYTOUN

281 8342911 P. 48

2001B053US

12

Fina 3371, available from Fina Oil and Chemical Co., a polypropylene
homopolymer.

ExxonMobil HD6704.67, available from ExxonMobil Chemical Co.,
Houston, TX, a high density polyethylene polymer.

Example 1

[0053] The coextruded biaxially oriented film structure is a polypropylene core
layer (Fina 3371), with a 26 gauge (6.5 micron) first sealant skin layer of Chisso
7701 that is contiguous to a first surface of the polypropylene core layer, and a
second skin layer of metallizable HDPE (ExxonMobil HD6704.67) that is
contiguous to a second surface of the polypropylene core layer. The total film
structure thickness is 90 gauge (23 micron). The first sealant skin layer contains
approximately 2,000 ppm of a non-migratory slip agent that is PMMA spheres
(EPOSTAR® MA 1010). The average particle size of the PMMA spheres is 10
micron. This film structure is also flame treated on the second skin layer
comprised of HDPE to improve adhesion of the aluminum to the film and to
optimize the lamination bond strengths.

[0054] The resultant biaxially oriented film structures have the following
properties tested immediately off the orienter. The orientation is 4.5 MD and 9
TD.

COF (U/U)

Additive Loading MST (U/U) Static Kinetic %Haze QTR
2000 ppm 217 F 0.88 0.83 6.20 2.00

Where U/U is untreated to untreated.

[0055] This film, metallizes well with substantially no blocking or winding
problems through orientation, slitting and metallization. The hermetic seal range
is feirly narrow on a Fuji Model FW-770 Packaging equipment at 50 PPM
(packages per minute). The hermetic crimp seal range is 40* F, and the hermetic
fin seal range is 10° F, The crimp seal strength is 1300-1550 gm/in in this
hermetic seal region, and the fin seal strength is 1900-2400 gm/in.

Received from < 281 8342911 > at 5M3 4:19:56 PM [Eastern Daylight me]

MAY-22-2003 15=49

ECLT BPlYTQUN

281 8342911 P. 49

2001B053US

13

Example 2

[0056] The second film structure is identical to the first example, except the first
sealant skin layer thickness is increased from 26 gauge (6.5 micron) to 40 gauge
(10 micron).

{0057] The resultant biaxially oriented film structures have the following
properties tested immediately off the orienter:

COF (U/U)

Additive Loading MSTQJ/U) Static Kinetic % Haze QTR
2000 ppra 219 F 0.90 0.84 6.60 2.35

|0058] This film, metallizes well with substantially no blocking or winding
problems through orientation, slitting and metallization. The hermetic seal range
is significantly greater than the product design in Example I on the Fuji 7700
Packaging equipment at 50 PPM. The hermetic crimp seal range is 50 F, and the
hermetic fin seal range is 30 F. The crimp seal strength is 2300-3000 gm/in in this
hermetic seal region, and the fin seal strength is 3000 gm/in or greater.
[0059] Although the present invention has been described in considerable detail
with reference to certain preferred embodiments thereof, other embodiments are
possible. For example, while multilayer films containing non-migratory slip are
exemplified at certain loadings and sizes, other loadings and sizes are
contemplated. Therefore, the spirit and scope of the appended claims should not
be limited to the description of the preferred embodiments contained herein.

Received from < 281 8342911 >at 5/22/034:19:56 PM [Eastern Daylight Timel